The FDA warns prenatal screening tests may give false results: What this means if you’re pregnant

Using a couple vials of blood from the mother’s arm, noninvasive prenatal screening, or NIPS tests, are considered much less invasive than diagnostic tests like amniocentesis or chorionic villus sampling, both of which come with a small risk of miscarriage. 

“While health care providers widely use NIPS tests, none have yet been authorized, cleared, or approved by the FDA,” states the agency in a press release. “The accuracy and performance of NIPS tests have not been evaluated by the FDA and these tests can give false results, such as reporting a genetic abnormality when the fetus does not actually have one.”

What is a NIPS test?

Initially designed to look for Down syndrome, NIPS tests, sometimes called noninvasive prenatal testing (NIPT), are screening tests, which means they can only report the risk of a fetus having a certain genetic abnormality. “They are not diagnostic tests, which are generally used to more definitively confirm or rule out a suspected genetic abnormality,” states the FDA.

Are NIPS tests accurate?

NIPS tests do have a high level of accuracy when screening for Down syndrome (98% to 99%), but when used to screen for incredibly rare chromosomal disorders, known as microdeletions, they may be wrong 85% of the time on average, reports The New York Times.

Put plainly, for every 15 times these tests correctly identify a problem, they incorrectly identify a problem a whopping 85 times.

But even if they get it right, the tests simply show an increased risk—not an actual diagnosis. 

Related: Should I get prenatal genetic screening?

NIPS tests do not diagnose a condition 

The tests are meant to be followed up by more invasive diagnostic testing later in pregnancy to confirm the results, which can be prohibitively expensive and come with a risk (albeit slight) of miscarriage. Amniocentesis, a diagnostic test which involves extracting a sample of the amniotic fluid, is usually performed between weeks 15 and 20 of pregnancy, which is past the point where abortions are legal in some states. The miscarriage risk of an amniocentesis test is 0.1% to 0.3%.

More than one-third of pregnant women undergo optional prenatal screening tests in their first trimester, according to the Times. Most insurance companies will cover NIPS testing automatically if you’re over the age of 35.

The American College of Obstetricians and Gynecologists (ACOG) recommends that NIPS testing be offered to all pregnant patients regardless of age or risk of chromosomal abnormality, but every patient has the option to decline.

And though healthcare providers are tasked with explaining that the tests simply highlight a possible heightened risk for a condition and not a definitive diagnosis, many women who undergo NIPS end up making decisions about their pregnancy after a positive result rather than undergoing follow-up diagnostic testing. 

That means plenty of women are having to make tough decisions about whether to carry their pregnancy to term based on incomplete—or potentially false—information. That’s a huge emotional burden to take on.

“The FDA is aware of reports that patients and health care providers have made critical health care decisions based on results from these screening tests alone and without additional confirmatory testing. Specifically, pregnant people have ended pregnancies based only on the results of NIPS tests. Without confirming the results with a diagnostic test, there is no way to know whether the fetus actually had the genetic abnormality reported by the screening test. The FDA is aware of cases where a screening test reported a genetic abnormality and a confirmatory diagnostic test later found that the fetus was healthy.”

These tests also prey on parents’ fears about having a child with a disability. While some genetic disorders can deeply impact quality of life, just because someone may be born with a genetic abnormality or disability doesn’t mean they won’t be able to lead a happy, fulfilling life. 

Related: The grief and gift of mothering a child with Down syndrome

Should you get NIPS testing? 

It may depend on your age, personal health history and family history, so always check with your doctor first. The FDA recommends understanding the benefits and risks of using NIPS tests and speaking with a genetic counselor or another healthcare provider before deciding whether to undergo these tests.

You should also not use the results of NIPS tests alone to make decisions about your pregnancy, warns the FDA. 

It’s also good to be informed about what the results mean.

What does a positive NIPS test result mean?

“A positive screening test result means that the fetus has a higher risk of having a genetic abnormality compared with the average risk. It does not mean that the fetus definitively has a genetic abnormality, or a condition caused by a genetic abnormality,” notes the FDA.

What does a negative NIPS test result mean?

“A negative screening test result means that the fetus has a lower risk of having a genetic abnormality compared with the average risk. It does not rule out the possibility that the fetus has a genetic abnormality, or a condition caused by a genetic abnormality,” notes the FDA.

“The ability of a NIPS test to correctly tell whether a fetus is at risk for a genetic abnormality depends on how common or rare the genetic abnormality is and on underlying risk factors. Disorders caused by a microdeletion (small missing piece of a chromosome) are rare. Because these conditions are so rare, a positive result may be more likely to be from a healthy fetus than one that actually has the reported genetic abnormality.”